United Nations Secretary-General Antonio Guterres described recent artillery and rocket fire around the Zaporizhzhia nuclear plant in central Ukraine as "suicidal," further adding to fears of an accident at the plant, which is the largest of its kind in Europe.
"Any attack on nuclear power plants is a suicidal thing," Guterres told reporters Monday in Tokyo. "I hope that these attacks will end," he said, and called on the International Atomic Energy Agency (IAEA) to be given access to the plant.
The Zaporizhzhia plant occupies an extensive site on the river Dnipro. It has continued operating at reduced capacity since Russian forces captured it early in March, with Ukrainian technicians remaining at work.
On Sunday, Ukraine's state energy company Energoatom said that one worker was injured by Russian shelling around the plant on Saturday.
Energoatom claimed that three radiation monitoring sensors were also damaged, saying "timely detection and response in case of aggravation of the radiation situation or leakage of radiation from spent nuclear fuel casks are currently impossible."
"This time a nuclear catastrophe was miraculously avoided, but miracles cannot last forever," the company added.
Speaking on Ukrainian television, Energoatom's chairman Petro Kotin said one strike Sunday was up to 20 meters away from the processed fuel storage area.
"If they had hit the containers with the processed fuel, it would be a radiation accident," he said.
Kotin suggested that if one container was hit "it will be a local accident on the territory of the plant and nearby territory. If it's two (or) three containers -- the affected area will increase."
Kotin also said that during the shelling, communication lines between the nuclear plant, the hydroelectric power plant and the Ukrainian energy system had been ruptured.
"As of now Zaporizhzhia NPP (nuclear power plant) is only connected to the Ukrainian energy system with just one communication line. If all the lines are damaged, the plant will transfer to the so-called 'black-out' mode, meaning become completely de-energized. And this situation will be very dangerous for keeping fuel in nuclear reactors in a safe condition," he said.
It was the second time in as many days that the plant was hit. Ukraine and Russia have traded blame for both attacks.
The Russian-backed authorities in the nearest city -- Enerhodar-- claimed that a Ukrainian missile landed within 400 meters of one of the plant's reactors. The city was seized by Russian forces at the same time as the power plant.
"Tonight, the armed formations of Ukraine struck with a Uragan 220 mm rocket missile cluster rocket," the local authority claimed, according to Russian state news agency RIA Novosti.
"Administrative buildings and the adjoining territory of the dry cask storage facility were damaged by the projectiles. It is important to note that the place of impact of warhead shrapnel and the rocket propulsion engine itself is no more than 400 meters from the active reactor," the authorities said.
CNN cannot verify claims made by either side. The Russians have been shelling the Ukrainian-held town of Nikopol from positions around the plant.
Fears about the security of Zaporizhzhia nuclear plant have been growing since Russian forces seized the site, but reached an inflection point on Friday when shelling damaged a high-voltage power line and forced one of the plant's reactors to stop operating -- despite no radioactive leak being detected.
After the attack, Energoatom said that Russian shellfire had damaged a nitrogen-oxygen station and the combined auxiliary building, and that there were "still risks of hydrogen leakage and sputtering of radioactive substances, and the fire hazard is also high."
On Saturday, the director general of the IAEA, Rafael Mariano Grossi, said he was extremely concerned by the shelling "which underlines the very real risk of a nuclear disaster that could threaten public health and the environment in Ukraine and beyond."
Ukrainian President Volodymyr Zelensky, who has accused Russia of using Zaporizhzhia nuclear power plant to wreak terror in Europe, said Sunday that he spoke with European Council President Charles Michel about the situation at the complex.
"Russian nuclear terror requires a stronger response from the international community - sanctions on the Russian nuclear industry and nuclear fuel," Zelensky tweeted.
The IAEA has been trying to coordinate a mission of safeguarding experts to visit the plant since it was seized by Russian forces. Yevhenii Tsymbaliuk, Ukraine's ambassador to the IAEA in Vienna, warned of catastrophic consequences if anything were to happen to the plant during a Monday press conference, saying it would not be "comparable even to Chernobyl or to Fukushima."
Tsymbaliuk said Ukraine would like to see a delegation of experts from the International Atomic Energy Agency and the United Nations visit the station to monitor its status but that Russia's military actions in Ukraine are making such a trip "impossible."